Synthetic lubricants



United States Patent 2,991,252 SYNTHETIC LUBRICANTS Samuel Richard Pethrick and Maurice B'arrington Sparke, both of Sunbury-on-Thames, England, assignors to The British Petroleum Company Limited, London, England, a corporation of Great Britain No Drawing. Filed Aug. 14, 1958, Ser. No. 754,931 Claims priority, application Great Britain Aug. 16, 1.957 10 Claims. (Cl. 252-475) This invention relates to synthetic lubricants.

Synthetic lubricants have previously been proposed consisting of a blend of a liquid aliphatic diester of a saturated aliphatic dicarboxylic acid and a polyester of the general formula:

HO(R OOCR COO) ,R OH I I where R is the hydrocarbon radical of an aliphatic dicarboxylic acid, R is the hydrocarbon radical of a glycol and n is a number from 1-10 (see UK. patent specification No. 763,077).

We have found now that certain blends of the above type or similar to the above type can be produced that have properties which render them particularly suitable for aero gas turbine lubrication.

According to the invention, a lubricating composition comprises a blend of a liquid aliphatic diester of a saturated aliphatic dicarboxylic acid and a polyester, soluble in the diester, and having the general Formula I above, where:

n is an integer,

the R s are alkylene groups having 4-14, preferably 6-10 carbon atoms, and

the R s are oxygenated hydrocarbon radicals of the formula:

-( z 2 )x z 6) 1) 2( 2 2)y- H where:

x is 0 or an integer, y is an integer and x+y does not exceed 5,

R is a methyl or ethyl group, preferably a methyl group,

and

R is an alkyl group having 1-4 carbon atoms, preferably a methyl group,

the relative proportions of diester and polyester in the blend being such that the viscosity of the blend at 210 F. is 3-30, preferably 3-10, especially 6-10 centistokes.

The alkyl and alkylene groups may be straightor branched-chain.

Preferred diesters for use in the blends according to the invention are those of the formula:

where R,- is an alkylene group having 4-14 carbon atoms and the R s are alkyl groups, preferably branch-chain having 4-18 carbon atoms.

Examples of suitable diesters are:

(i) Di(2-ethyl hexyl) sebacate; (di-octyl sebacate) (ii) Di(3:5:5-trimethylhexyl) sebacate; (di-nonyl sebacate) (iii) 2-ethylhex1yl(3z5z5-trimethylhexyl) sebacate; (octyl nonyl sebacate), and

(iv) Mixtures of (i), (ii) and (iii).

Preferred polyesters are those having a viscosity at 25 C. of 50-20,000 centistokes, especially 500-l0,000 centistokes, particularly those in which the R s have 7 or 8 carbon atoms, especially octamethylene, 1:1:3-tn'methyl- ICC tetramethylene or 1z3z3-trimethyltetramethylene, and the R s are radicals of Formula II in which x+y=12.

It is to be understood that different R groups, different R groups, different R groups and different values of x and y may be present in any given polyester molecule, that different R groups may be present in any given diester molecule and that mixtures of different polyester molecules and/or different diester molecules may be present in the same blend.

Polyesters for use in the lubricant blend according to the invention may be prepared by reacting in one or more stages the following ingredients:

(a) an acid or acids of the formula HOOCR COOH, and (b) a diol or diols of the formula HO (CH CH O) CI-I C (R (R CH OCH CH OH III Where R R R x and y have the values given previously, the molecular proportion of diol(s) being greater than, but preferably not more than twice, the molecular propor tion of acid(s). Diols of Formula III may be prepared by reacting ethylene oxide with a diol of the formula HOCH C(R (R CH OH the molecular ratio of ethylene oxide to diol not exceeding 5:1 and being preferably 1-2:1. As stated above, mixtures of polyesters of the above formula may be used in the lubricant blend i.e. polyesters having different values of n and having different acid and diol residues. With such a mixture the average value of It would not necessarily of course be a whole number. Thus when preparing a polyester mixture, the molecular proportions of the ingredients to be reacted need not be present in whole number ratios.

Examples of acids which may be used in the preparation of the polyesters are adipic acid, pimelic acid, suberic acid, azeleic acid and brassylic acid.

Particularly satisfactory acids have been found to be:

(a) sebacic acid, and (b) an equimolecular mixture of 2:2:4-trimethyladipic,

2:4:4-trimethyladipic and sebacic acids.

Particularly satisfactory diols were prepared as follows: 416 gm. (4 mol) of neopentyl glycol (2:2-dimethyl- 1:3-propanediol) was heated to C. and a small quantity of zinc chloride (a catalyst) was stirred in. Ethylene oxide was then passed through the hot mixture until 310 gm. (about 7 mol) of ethylene oxide had combined with the neopentyl glycol. The pressure was then reduced to 1 mm. ofmercury and the diol product distilling off over the temperature range 60-145 C. was collected. The molecular weight of the diol product (hereinafter called diol D1) was and it consisted mainly of a mixture of diols of Formula 111 in which R and R are methyl groups and x-l-y had an average value of about 1.7.

Some of the diol D1 was further distilled until a diol product (hereinafter called diol D2) was obtained which had the following properties:

Boiling point l32.7 C. at 9.5 mm. Hg. n 1.4482. Analysis C, 56.75%; H, 10.7%.

These properties correspond to a formula of C H O i.e. a compound of Formula III in which R and R are both methyl groups, x=0 and 31:1.

Preferably the blend according to the invention is one containing 560% by weight of polyester, especially 5-35 the remainder of the blend being substantially diester.

Any antioxidant for lubricants, for example phenothiazine, may be incorporated in the blend if desired.

By way of example, polyesters P121, P122 and P131 were prepared from the ingredients listed in Table 1 below by the following method:

The ingredients were reacted in a three-neck, 500 ml. flask fitted with a stirrer, a nitrogen inlet tube and a vertical steam-heated condenser fitted to a water-cooled, downward facing condenser. Nitrogen was blown through at a rate of approximately 5 liters per hour and the following heating cycle carried out.

The contents of the flask were heated rapidly to 130 C. (all temperatures being measured internally) at which they were kept for four hours. After the reaction had been allowed to continue at each of the temperatures 150, 180 and 200 C. for two hours, the distillate was collected. The diol content was calculated from a refractive index determination and, after this amount had been added to the flask, heating at 240 C. was carried out until the acid value fell below 5 mg. KOH/g. At this stage the pressure was reduced to 17 mm. of mercury and the reaction was continued at 240 C. until the acid value fell below 1 mg. KOH/ g.

Table I gives the composition and properties of polyesters P121, P122 and P131.

Table I Molar Proportions Viscosity at C. Polyester (centi- Sebacie Mixed Diol Diol stokes) Acid Acids 1 D1 D2 1 A11 equimolecular mixture of 2:2:4-trimethyladipic, 2:4:4-trimethyladipic and sebaeie acids.

10 The open beaker test referred to in Table H was carried out as follows. 250 ml. of oil are heated in a 400 m1. beaker in an oven maintained at an air temperature of 300 C. Samples of the oil are withdrawn after heating for 2, 3, 4 and 5 hours and the viscosity at 100 F. is

15 measured.

We claim: 1. A lubricating composition consisting essentially of a blend of:

a liquid aliphatic diester of the formula R OOCR COOR where R is an alkylene group having 4-14 carbon atoms and R is an alkyl group having 4-18 carbon atoms, and

5-60% by weight of the composition of a polyester which is soluble in the diester and has the general formula n is an integer, R is an alkylene group having 6-10 carbon atoms, and R is an oxygenated hydrocarbon radical of the formula (CH CH O CH C CH CH OCH CH y where:

x is an integer from 0-4, 1 is an integer from 1-5 and x-i-y does not exceed 5,

the viscosity of the polyester at 25 C. being -20,000

centistokes,

the relative proportions of diester and polyester in the blend being such that the viscosity of the blend at 210 F. is 3-10 centistokes.

2. A lubricating composition according to claim 1 in cluding an anti-oxidizing amount of phenothiazine.

3. A lubricating composition consisting essentially of a blend of:

at least one diester selected from the group consisting of di(2-ethylhexy1) sebacate, di(3:5:S-trimethylhexyl) methylhexanol. In addition to octyl nonyl sebacate, the sebacate and 2-ethylhexyl(3 5 :S-trimethylhexyl) sebaproduct also contained di-octyl and di-nonyl sebacates. 50 cate, and

Table II Ingredients of blends, percent wt. Thermal Stability (open Viscosity Viscosity Low Temperature beaker test), Blend at 210 F., at 100 F., Performance Max. change Diester Polyester Phenocentistokes centistokes in viscosity thiazine at 100 F.,

percent 80. 41 18.59 (P121)- l. 0 7. 83 37. 21 Mobile at -50 C +14. 9 80. 07 16.93 (P122) 1. O 7. 9 37. 12 Mobile at C 80. 71 18.29 (P131)... 1. 0 7. 76 37. 82 Mobile at -54 C +16. 5 91. 46 7.51 (P61)- 1. 0 6. 5 2B. 36 Immobile at 40 C- -20. 2 7.51 35.85 Immobile at 40 C the less viscous diester component than blends B121 and 5-35 by weight of the composition of a polyester which is soluble in the diester and has the general formula HO (R OOCR COO) R OH where:

n is an integer,

R is an alkylene group having 7-8 carbon atoms, and R is an oxygenated hydrocarbon radical of the formula 5 t where:

x is an integer from -1, y is an integer from 1-2 and x+y equals 1-2,

the viscosity of the polyester at 25 C. being 500-10,000

centistokes,

the relative proportions of diester and polyester in the blend being such that the viscosity of the blend at 210 F. is 6-10 centistokes.

4. A lubricating composition according to claim 3 in which the polyester is one in which R is a radical selected from the group consisting of octamethylene, 1:1:3- trimethyltetramethylene and 1 :3 3-trimethyltetramethylene.

5. A lubricating composition according to claim 3 including about 1% by weight of the composition of phenothiazine.

6. A lubricating composition consisting essentially of:

a liquid aliphatic diester of the formula R OOOR COOR where R is an alkylene group having 4-14 carbon atoms and R is an alkyl group having 4-18 carbon atoms, and

5-60% by weight of the composition of a polyester which is soluble in the diester and which has been prepared by reacting an acid of the formula HOOOR COOH where R; is an alkylene group having 6-10 carbon atoms, with a diol of the formula:

H0 (CH CH O) CH C (CH 0H; OCH CH 0H where:

x is an integer from 0-4, y is an an integer from 1-5 and x-l-y does not exceed 5, the molecular proportion of diol being greater than, but not more than twice, the molecular proportion of acid,

the viscosity of the polyester at 25 C. being 50-20,000

centistokes,

the relative proportions of diester and polyester in the blend being such that the viscosity of the blend at 210 F. is 3-10 centistokes.

7. A lubricating composition according to claim 6 including an anti-oxidizing amount of phenothiazine.

HOOCR COOH where R is an alkylene group having 7-8 carbon atoms, with a diol of the formula HO(CH CH O) CH C(CH CHMOCH CH OH where x is an integer from 0-1, y is an integer from 1-2 and x+y equals 1-2, the molecular proportion of the diol being greater than, but not more than twice, the molecular proportion of the acid, the viscosity of the polyester at 25 C. being SOD-10,000 centistokes,

and the relative proportions of diester and polyester in the blend being such that the viscosity of the blend at 210 F. is 6-10 centistokes.

9. A lubricating composition according to claim 8, in which the acid is one in which R is a radical selected from: the group consisting of octamethylene, 1:1:3-trimethyltetramethylene and 1 :3 :3-trimethyltetramethylene.

10. A lubricating composition according to claim 8 including about 1% by weight of the composition of phenothiazine.

References Cited in the file of this patent UNITED STATES PATENTS 2,499,983 Beavers -n ..i Mar. 7, 1950 2,499,984 Beavers et al. Mar. 7, 1950 2,820,815 Matuszak et al. a- Jan. 21, 1958 FOREIGN PATENTS 763,077 Great Britain a Dec. 5, 1956 786,767 Great Britain i t Nov. 27, 1957 790,923 Great Britain Feb. 19, 1958 OTHER REFERENCES I. and B. Chem, December 1950, vol. 42, No. 12 page 2415.

Lubrication Engineering, August 1957, pgs. 454-458. 

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF
 1. IN A PROCESS FOR THE PRODUCTION OF SODIUM AND POTASSIUM SALTS OF HYPOSULPHUROUS ACID BY THE REDUCTION A BLEND OF: A LIQUID ALIPHATIC DIESTER OF THE FORMULA R4OOCR5COOR4 OF THE SO2-ION IN AQUEOUS SOLUTION, THE STEP WHICH COMPRISES REDUCING THE SO2-ION BY MEANS OF A BOROHYDRIDE WHERE R5 IS AN ALKYLENE GROUP HAVING 4-14 CARBON ATOMS AND R4 IS AN ALKYL GROUP HAVING 4-18 CARBON WHICH IS A MEMBER SELECTED FROM THE GROUP CONSISTING OF SODIUM AND POTASSIUM BOROHYDRIDE. ATOMS, AND 5-60% BY WEIGHT OF THE COMPOSITION OF A POLYESTER WHICH IS SOLUBLE IN THE DIESTER AND HAS THE GENERAL FORMULA 